1. Field of the Invention
In general, this invention pertains to locksmiths' tools and methods, and in particular, to a method and apparatus for determining the combination of a locked safe of a particular, known type without the destruction of the lock or safe.
2. Description of the Related Art
A conventional combination lock typically comprises a plurality of tumbler wheels which are coaxially journaled on a rotating spindle which projects outwardly from the lock and mounts a lock dial having a plurality of calibration marks thereon opposed to a dial ring having a index mark opposed to the calibrations. The spindle is rotatably coupled to the tumbler wheels through a lost-motion connection such that each of the tumbler wheels may be driven upon a predetermined rotation of the spindle. Each of the tumbler wheels and a drive cam mounted coaxially with the wheels are provided with a circumferential gate at a selected radial position.
A fence lever pivotally connected at one end to a sliding bolt has a nose part at the opposite end which is designed to reside on the drive cam periphery and a fence projecting laterally in overlying relation with the peripheries of the tumbler wheels. When the tumbler wheel gates are out of alignment with the fence, contact of the fence with the outer periphery of the tumbler wheels prevents the nose of the fence lever from engaging in the gate of the drive cam, and it is only when the tumbler wheels have been aligned by their manipulation in a predetermined, sequential order of angular displacements that the fence lever will engage the gates and permit the nose part to engage the drive cam, thereby permitting the bolt to be drawn by a rotation of the spindle.
A variation on such a lock is discussed in U.S. Pat. No. 3,968,667 to Gartner, et al.
It occasionally falls to the locksmith to open a locked safe mounting such a lock when either the combination is unavailable or in the case of lock malfunction. The safe may be opened either by manipulation or by forced entry. The advantage to manipulation is that it does not damage the safe or its contents, either of which may be very valuable. However, the disadvantage is that the technique is not easy to master. In attempting to drill the lock open, exact calculations are required to determine the correct drilling location. Additionally, a variety of scopes, templates, lights and other tools are frequently necessary. Finally, the opening procedure usually boils down to a tedious, time-consuming, "hit-or-miss" proposition, as the locksmith attempts to manipulate the gates of the wheels into simultaneous alignment with the fence of the lock.